Matsya Purana — Nārāyaṇa as Haṃsa in the Cosmic Ocean: Vedic Yajña-Puruṣa and Mārkaṇḍeya’s Vi...
ददर्श चापि पुरुषं स्वपन्तं पर्वतोपमम् सलिले ऽर्धमथो मग्नं जीमूतमिव सागरे //
dadarśa cāpi puruṣaṃ svapantaṃ parvatopamam salile 'rdhamatho magnaṃ jīmūtamiva sāgare //
He also beheld a man, asleep and mountain-like in form—half-submerged in the water—like a mass of clouds resting upon the sea.
It uses vivid pralaya imagery: a being lies in a sleep-like state while the world is water-covered, suggesting cosmic suspension and dissolution where forms appear half-submerged in the deluge.
Indirectly: it underscores impermanence during pralaya, reinforcing the Matsya Purana’s ethical thrust that kings and householders should uphold dharma and prepare through righteous conduct, since worldly stability can vanish like a flood.
No direct Vastu or ritual rule is stated; the verse is primarily descriptive, offering symbolic imagery (sleep, submergence, ocean) sometimes used by later tradition to frame rites of protection and renewal after calamity.